Latitude:
40° 26' 23"N

Age:

Formation(s):

Purpose:

This site provides one of the best views of the Historic and
geologically significant Point of Pittsburgh.

Access and Parking:

Park on nearest side street (Sweetbrier St.) and walk across
Grandview Avenue to overlook. Parking for motor coach with prior permission from
local businesses (Monterey Bay Fish Grotto) or residents. Recommended for all
age groups.

From Oakland, take any bus to downtown Pittsburgh.
Then either walk across Smithfield Street Bridge or take T to Station
Square. The take Duquesne incline or Monongahela Incline to Grandview
Avenue. Walk to site. Return.

Driving Directions:

From the Cathedral of Learning, Drive 0.7 mi. west on
Fifth Avenue. Make a Left on Craft Av. Go 0.1 mi., then make a right onto
Blvd. of Allies, go 1.6 mi. then follow signs to Liberty Bridge and into the
Liberty Tunnel. BEFORE entering tunnel, make a right onto McArdle Roadway
and follow up to Grandview Avenue. Go 0.5 miles along Grandview Avenue and
park as directed above.

See map and figures.

What you will see:

“The Point” refers
to the location where the Monongahela River and the Allegheny River merge to
create the Ohio River in the area that is now downtown Pittsburgh. With the
coming of European settlers in the mid 1700s, The Point became a strategic
location in protecting the frontier, first for the French with Fort Duquesne and
later for the British with Fort Mercer and Fort Pitt. During the 1800s and early
1900s, the Point area became an industrial complex and the center of the
American steel industry. Today, the Point is the focus of the transition of
Pittsburgh from an industrial giant to that of a financial and cultural center.

As you look out
from this vantage point, you will see the relative flat Southside, Downtown,
North Side, and, to the west, Brunot Island. The flat areas are all underlain by
glacial sands and gravels and later river gravels. The flat area abruptly
terminate against the adjacent hills such as Mt. Washington (on which you are
now standing). Imagine, if you will, that during the Pleistocene glacial events,
meltwater from glaciers just 50 km to the north flowed into the Pittsburgh area
and possibly covered much of the lowlands you see with shifting, braided rivers
and occasional meltwater lakes.

Geologic History:

George Washington wrote in his Journal
(1754):

“As I got down
before the Canoe, I spent some Time in viewing the Rivers, and the Land in the
Fork; which I think extremely well situated for a Fort, as it has the absolute
Command of both Rivers. The Land at the Point is 20 to 25 Feet above the common
surface of the Water; and a considerable Bottom of flat, well timbered Land all
around it, very convenient for Building: The Rivers are each a Quarter of a
Mile, or more across, and run here at very near right Angles: Aligany N.E. and
Monongahela S.E. The former of these two is very rapid and swift running Water;
The other deep and still, without any perceptible Fall.”

The Point is located at the confluence of
two major Rivers, the Allegheny, which drains much of northwestern Pennsylvania,
and the Monongahela which drains much of southwestern Pennsylvania and northern
West Virginia. These two major rivers meet to form the Ohio River, which then
flows, first northwestward, then southwestward toward the Mississippi River.
However, as pointed by Leverett (1934), Wagner and others (1970), and Harper
(1997,
http://www.dcnr.state.pa.us/topogeo/pub/v28n3-4.pdf) the configuration of
the rivers has not always been as we see it today. The Allegheny River has
changed markedly since the period of continental glaciation that covered much of
northern North America (below). (http://www.watershedatlas.org/watershed/fs_create.html).
Similarly, the Monongahela River has changes its course many times over the
history of the river. To view a map of the ancient courses of the river see
http://www.watershedatlas.org/watershed/fs_meander.html.

Figure from Harper (1997). Map showing the
configuration of the rivers in Western Pennsylvania before the Ice Age. Note
that the Upper Allegheny and Middle Allegheny Rivers flowed northward toward the
St. Lawrence River, as did the Ohio River. The presence of the ice sheets caused
the rivers to change to their modern courses.

Today, in
Pittsburgh, the rivers flow over an accumulation of glacial sediments (sand and
gravel) that were deposited during the last Ice Age when glaciers advanced as
far south as Slippery Rock, PA Figure above). During that time, glacial
meltwater significantly added to the volume of water flowing in the Allegheny
river. The river valleys were consequently widened and their floors covered with
a thick blanket of debris that had been washed out of the ice. Since that time,
the rivers have deposited a layer of fluvial (river derived) sediments as
floodplain deposits.

These deposits
make up downtown Pittsburgh, the Southside, and much of the North Side. Beneath
the layers of glacial and fluvial sediment is Pennsylvanian age (~280 – 300
million year old) bedrock consisting of shale, sandstone, limestone, and coal
that were originally deposited in ancient coal swamps, freshwater lakes, and
occasional marine (ocean) transgressions. The Point area in underlain by the
Conemaugh Group or ‘the upper barren measures’ (referring to the general lack of
minable coals in the unit). To the east and south, the higher elevations
(generally above 900’) are underlain by the Monongahela Group or ‘the upper
productive measures’ (referring to the productive Pittsburgh Coal horizon that
separate the two groups).

Figure from
Harper (1997). Development of the Allegheny and Monongahela River valleys over
the past 1 million years, as shown in cross section. Sections A-C show how the
rivers eroded downward as the land rebounded after being ‘weighed down’ with
glacial ice. Note that in the area that is now Downtown Pittsburgh is underlain
by a blanket of glacial sand and gravel then a layer of more recent nonglacial
river deposits such as sand silt and clay.

Pittsburgh Then and Now

Some of the earliest descriptions and
contemporary drawings of the point area are from the time of Fort Duquesne which
was built on the site in 1754. The figure below shows a drawing done during or
soon after the fort was built, presumably by Capitan François Le Mercier, who
was the engineer in charge of construction (Stotz, 1985). This plan shows a
sharp point of land at the Point with erosional bluffs along the river banks.
The river banks are not straight, but have a concave erosional pattern. A later
drawing by Joseph Gaspard Chaussegros de Léry (below), King Louis XV’s chief
engineer in Canada also shows the bluffs, but the river banks appear straighter
than in the earlier map. In 1758, J.C. Pleydell, an engineer with the British
army made a plan of the fort that shows the morphology of the Point quite well,
especially the steep bluffs along the banks. The height of the bluffs is not
known precisely, but Stotz (1985) mentions that they were “15 to 20 feet high
and were rutted by erosion, exposing glacial clay, sand and gravel that composed
the soil.” John McKinney, an English prisoner at Fort Duquesne described the
area immediately east of the fort in these words:

“There is no bogs or
morasses near the fort, but good dry ground, which is cleared for some distance
from the fort, and the stumps cut close to the ground; a little without musket
shot of the fort in the fork is a thick wood of some bigness full of large
timber” (Stotz, 1985).

Although occasionally flooded, the Point was
not a marsh, but high dry land. From these drawings and descriptions, Stotz
(1985) prepared an artist’s rendering of the Point during Fort Duquesne time.
Using these descriptions and maps as well as later maps, Laurent (1980) provided
an artist’s rendering of an even earlier, pre-Fort Duquesne view of the Point.

Plan of Fort Duquesne made by Capitan
François Le Mercier (circa 1754-1755). From Stotz (1985). Note the irregular
shoreline and the steep bluffs. During this time period, the ‘Allegheny River’
was still referred to as Rivere D’Ohio ou Belle Rivere (Ohio River or Beautiful
River).

Map of Fort Duquesne and environs
made by Léry in 1755. From Stotz (1985). Note the very accurate and careful
measurements of the river widths

In 1819, Riddle and Murray (1819) described
the Pittsburgh area as follows:

“The ground upon
which Pittsburgh is built is nearly level and bout forty feet (on an average)
higher than the surface of the river at low water… Besides the tableland, which
constitutes the principle part of the city, there were, in the year 1780, two
parallel flats upon the Allegheny shore, each about 300 yards broad, extending
half a mile from the Pittsburgh Point. The lowest of these, that is, the one
next to the river, has been entirely washed away, together with a considerable
portion of the second. At the same time (1780) there stood near the shore of the
outer flat a row of handsome buildings which were erected for the reception of
Indian traders. One portion of the row had been demolished as it was supposed to
stand in an inconvenient position with regard to the fort, and the other part
was presently precipitated into the Allegheny.”

By taking information from the old pre-1800
maps of the Point, two overlay reconstructions have been made to visualize where
the river shorelines, islands, and ponds were in colonial times with respect to
modern-day Pittsburgh. The figure to the right below shows a close-up of the
point and the location of the point as it was in the late 1700s. Note how small
the point was then compared to today. If we look at the entire downtown
Pittsburgh region, we see the location of the Islands on the North side with
respect to the present position of the Carnegie Science Center and the former
location of Three Rivers Stadium. Also, note the locations of Hogg Pond and
other ponds in downtown Pittsburgh as well as the island in the Monongahela
River. Compare the 1795 and 1815 maps with the recent air photo:

1795
1815
Today

Islands

There are many islands (http://watershedatlas.org/lowerallegheny/fs_natsys3.html)
throughout the Allegheny, Monongahela and Ohio Rivers in the Pittsburgh area.
One of the primary functions of rivers is to transport sediments from the
headwaters to lower elevations. The source of the sediments is usually erosion
of soil and weathered rock fragments, but may also be glacially-deposited
sediments as in the case of the Allegheny River. During periods of high velocity
flow, especially during flooding event, the river can transport large amounts of
sediment. As floodwaters recede and velocities drop, the sediment is deposited.
Islands begin with the slow accumulation of sand and gravel deposited over years
of flooding. Eventually, these accumulations break the surface of the stream or
river to form an island. Along with the deposition of sand and gravel,
silt and clay accumulates among the interstices, the pores spaces between
gravel, and becomes the soil medium that supports the growth of subaquatic
vegetation, grasses, shrubs, and eventually trees. The plant species found on
islands are well adapted to full sun, moist to wet soils, and seasonal flooding.
Sycamore trees and alder shrubs are common woody plants found on islands.

Once an island is established, erosion begins to work
on both the upstream and downstream tips of the island. If the island is
predominantly gravel, it will last a long time. If the composition of the island
is mainly sand and silt, however, one can readily witness the erosion of its
upstream and downstream tips over a fairly short time. Islands are ephemeral,
instream landscape features; they grow with deposition, and wash away with
erosion. Islands in the three rivers come in many sizes. Some are ten acres or
less, while others, like Neville Island, can be hundreds of acres.

Islands Here and
Islands Gone

Kilbuck
Island

On all early maps and drawing of Pittsburgh,
an island, or in some cases a series of islands are shown in the vicinity of the
present-day Carnegie Science Center and Heinz Field. Although not shown on any
earlier maps, the island across the Allegheny from the Point was first referred
to by Léry in 1755. He described on his drawing “…an island which is a peninsula
when the water is at medium…” A single large island is shown on Elais Meyer’s
1761 map. A sand bar, presumably covered at high water, connects it to the north
shore much as described by Léry. The 1795 map (above) shows two islands and a
small peninsula, the larger island is called Smokey Island. The Plan of
Pittsburgh from a 1796 engraving by Tardieu L’Aine does not show any islands,
but the accuracy of the north shore area depiction is in question as there
appears to be a stream shown in the area of the islands that is hidden by the
figure caption. The 1815 Darby map and the 1825-1826 the map of the area shows
three islands (Kilbuck, Low, and a small unnamed island) and a ‘sand bar at low
water.’ The 1825-1826 map appears to be a derivation of the 1815 map because the
shapes of the islands are nearly the same. A good contemporary view of Smokey
island is shown in an 1817 sketch drawn by Mrs. E. C. Gibson, member of the
Philadelphia Bar while on her wedding journey (Laurent, 1980). By 1850, a map of
Allegheny City by Day and Cramer (From Cowin, 1985) shows that Smokey or Kilbuck
Island is again now just a peninsula off of the North Side.

By the early 1900s, the backwaters behind
the islands was filled in to make room for industrial development on the North
Side.

The Island in the Mon

The 1795 (above) and 1815 (above) maps both
show a large island in the middle of the Monongahela river The large sand bar
was used as buckwheat fields in the late 1700s. Significantly, the island so
well depicted on the 1795 and 1815 maps is not present on any earlier maps
(Figures II-18 and II-23 in Stotz (1985)), Elias Meyer’s 1761 map nor on the
first sketch of Pittsburgh drawn in 1794 by Louis Brantz, a Philadelphia
merchant). This suggests that a major flooding event between 1794 – 1795
deposited the material that was to become the island. The island then persisted
to at least 1815. A sketch of Pittsburgh in 1817 does not show the island.
However, the 1825-1826 map by H. H. Bernhard, Duke of Saxe-Weimar Eisenach shows
the island as a “sand bar dry at low water,” but again, this just may be a copy
of the 1805 map.

Wainwrights Island

Wainwrights
Island was located in the Allegheny River adjacent to what is now Lawrenceville.
http://www.clpgh.org/exhibit/neighborhoods/lawrenceville/lawb.html. In the
words of Fleming (1915) “Wainwright's Island [has] long since wasted away, [but]
it was on this island that [Christopher] Gist and [George] Washington landed
after their perilous voyage across the Allegheny, full of heavy floating ice, on
an improvised raft in 1753, while returning from their mission to the French
commander, St. Pierre, at LeBoef, now Waterford, Pa. Washington records in his
journal December 27, 1753, that they built the raft with one poor hatchet and
finished after sunset, putting a whole day in the work. The next day they
launched it and getting aboard, pushed it off. He [Washington] continues:

“Before we were half way over we were
jammed in the ice and in such a manner that we expected every moment our raft to
sink and ourselves to perish. I put out my setting pole to try and stop the raft
that the ice might pass by, when the rapidity of the stream threw it with so
much violence against the pole that it jerked me out into 10 feet of water, but
fortunately, I saved myself by catching hold of one of the raft logs.
Notwithstanding all our efforts, we could not get to either shore, but were
obliged as we were near an island to quit our raft and make for it.“

The two put in a miserable night, Gist
having his fingers and toes frozen, but the channel between the island and bank
froze so hard they had no difficulty in crossing in the morning and then made
their way to the cabin of John Frazier, the English trader on the Monongahela,
at the mouth of Turtle Creek.”

Most likely the narrow backwater between
Wainwrights Island and Lawrenceville was filled in the late 1800s to make more
land for development. However, it is still shown on an 1863 map showing the
“Defenses of Pittsburgh” (Cowin, 1985, page 317).

Today, in the vicinity of Pittsburgh, there
are three islands in the Ohio River (Brunot Island, Davis Island, and Neville
Island) and six in the Allegheny River (Herrs Island, Sixmile Isalnd [located
six miles from the point], Sycamore Island, Ninemile Isalnd, Twelvemile Island,
and Fourteenmile Island). There are no islands in the Monongahela River near
Pittsburgh. The large number of islands in the Allegheny is a reflection of the
large amount of glacially-derived sediment that was moved by the river. For an
interesting coverage of the Ohio River Islands see Ferrick-Roman (2001).

Anthropogenic changes in the Point area:

As Pittsburgh became a center for river
commerce during the Industrial Revolution, the fickle nature of river flow
continued to plague riverboat captains. Even into the late 1800s, the
Monongahela Wharf (Figures 20 and 21) area along the south side of the city was
commonly an area used for boats to wait out periods of low flow before starting
or continuing their journey.

nTo remedy this problem, locks and dams were
constructed to maintain pool level and river flow.

nIn 1837, The Monongahela Navigation Company,
chartered by the Commonwealth of Pennsylvania, began building a series of seven
locks and dams from Pittsburgh to the West Virginia state line.

nLock and Dam No. 1 was located one mile from
the Smithfield Street Bridge along the Monongahela River

nLock and Dam No. 2 was located at Braddock’s
Upper Ripple, above the mouth of Turtle Creek, approximately 10 miles from No.
1, also along the Monongahela River

nTo minimize river bank erosion, seawalls
have been constructed along much of the urban river shoreline.

nMany physiographical and topographical
features described by travelers and early settlers, and depicted in early maps
have been covered with fill during periods of urbanization and redevelopment.

Click on the thumbnails below for pictures:

A view of the Point and City of
Pittsburgh. The point is an accumulation of non-glacial river gravels.

This photo is a pan to the
northeast of the city, showing the North Side.

A further pan to the north of the
city. The flat area is underlain by glacial sands and gravels.

Roberts, P. ed., 1996, Points in Time: Building a Life in
Western Pennsylvania: Historical Society of Western Pennsylvania, Pittsburgh,
PA, 124 p.

Stotz, C. M., 1985, Outposts of the War for Empire, The
French and English in Western Pennsylvania: Their Armies, Their Forts, Their
People, 1749-1764: Historical Society of Western Pennsylvania, Pittsburgh, PA,
203 p.

Schafer, J., and Sanja, M., 1992, The Allegheny River:
Watershed of the Nation, The Pennsylvania State University Press, Unversity
Park, Pennsylvania, 304 p.